CN102111255A - Adaptive error detection method used for cellular mobile communication system - Google Patents

Abstract

The invention discloses an adaptive error detection method used for a cellular mobile communication system. The method comprises the following steps of: respectively performing time interval (TI) sampling used for calculating the time interval of received two adjacent protocol data units (PDUs) and TI smoothing used for realizing filtering in a radio link control protocol layer entity; performing round trip time (RTT) sampling used for acquiring a round-trip delay of each protocol data unit (PDU), RTT smoothing used for realizing the filtering, k sampling used for acquiring the repeat number of each error protocol data unit, and k smoothing used for realizing the filtering in a medium access control (MAC) layer; and setting a time-out value of a reordering timer. The method detects the lost packets of the MAC layer accurately and timely, avoids unnecessary repeat of radio link control (RLC), and reduces the repeat delay of the packets by adaptively estimating the repeat time of MAC PDU and optimizing a t-reordering value of a selective repeat-automatic repeat request (SR-ARQ). By using the method, low complexity is realized without increasing the overhead of an air interface of a radio link.

Description

The adaptive error detection method that is used for cell mobile communication systems

Technical field

The invention belongs to moving communicating field, specifically is a kind of error detecting method that is used for cell mobile communication systems.

Background technology

The evolution thinking of the third generation mobile communication system mainly is by adopting high-order modulating and various effective channel coding technology, constantly strengthen the data transmission capabilities of air interface, finally make wave point and core network all move towards IP (Internet Protocol) and change.

Because the wave point of mobile communications network partly adopts wireless transmission method, compares with cable network, radio communication has the high characteristics of the error rate, and this will increase the Loss Rate of packet, and cause the burst packet loss.High packet loss is the performance of deterioration upper-layer protocol, thereby influences the quality of data service, especially can reduce the performance of the transmission control protocol (TCP, Transmission Control Protocol) of transport layer.For this reason, the air interface of cell mobile communication systems can adopt the error correction coding with strong error correcting capability usually, to reduce the packet loss of wave point.But error correction coding can be brought extra expense, and error correcting capability is strong more, and this expense is expensive more.Simultaneously, because the feature of wireless channel is to change in time, require coding and modulation state dynamic change, therefore along with channel, the physical layer of the air interface of the third generation mobile communication system adopts adaptive coding and modulation technique (AMC, Adaptive Modulation and Coding).

AMC can adapt to the dynamic change of quality of wireless channel, in the error rate that reduces air wireless interface, improves the utilance of wireless frequency spectrum.Yet even adopt the AMC technology, the air wireless interface of cell mobile communication systems still has higher packet loss, can not satisfy upper-layer protocol.For this reason, cell mobile communication systems of new generation adopts automatic repeat requests (ARQ, Automatic Repeat reQuest) technology at the link layer of wave point, further reduces the packet loss of wave point.

At Wideband Code Division Multiple Access (WCDMA) (WCDMA, Wideband Code Division Multiple Access) evolution version is (among the R5～R9), medium access control (the MAC of its wave point, Medium Access Control) layer and radio link control (RLC, Radio Link Control) layer has all adopted the ARQ technology.Wherein the MAC layer is with traditional forward error correction (FEC, Forward Error Correction) and the combination of ARQ technology, transmit leg is by positive acknowledgement/Negative Acknowledgement (ACK/NACK of recipient's feedback, ACKnowledgement/Non-ACKnowledgement) whether decision retransmits, and when retransmitting, adopt the various channel conditions of method self adaptation of steadily increase redundancy (IR:Incremental Redundancy), elevator system performance.Rlc layer adopts selects retransmission mechanism (SR-ARQ:Selective Repeat ARQ), and the recipient tells grouping serial number and the wrong grouping serial number that transmit leg correctly receives by ACK/NACK, and transmit leg only retransmits wrong grouping.

The evolution version of WCDMA adopts the main purpose of SR-ARQ to be to correct the residual error of mixing automatic repeat requests (HARQ, Hybrid ARQ) at rlc layer, with further reduction packet loss.In order to correct the residual error of HARQ, recipient's SR-ARQ must judge at first which is grouped among the HARQ of MAC layer and correctly do not retransmitted.For this reason, the SR-ARQ of RLC unites the out-of-sequence detection of use and resets timer (t-Reordering) timeout mechanism and detect the grouping of losing at the MAC layer, as shown in Figure 1: the t in Fig. 1 ₁Constantly, the recipient (can be subscriber equipment (UE:user equipment) or evolution base station (eNB:evolved Node-B), corresponding transmit leg is eNB or UE, down with) to receive sequence number (SN:Sequence Number) be 5 grouping, because being 4 grouping, sequence number loses, therefore, this moment VR (R)＜VR (H) (VR (R): next sequence number of dividing into groups according to the order of sequence of receiving of expectation; VR (H): the maximum sequence number that has received grouping adds 1).After finding VR (R)＜VR (H), the recipient starts rearrangement timer (t-Reordering), waits for that the HARQ of MAC layer retransmits, at t ₂Constantly, retransmission timer is overtime, t ₂-t ₁Be the value of retransmission timer.When t-Reordering overtime, receive direction transmit leg status report (STATUS) is divided into groups, and ACK sequence number (ACK-SN) and NACK sequence number (NACK-SN) are set to 6 and 4 respectively, after the recipient receives the STATUS grouping, the selection retransmission sequence number is 4 grouping, thereby realizes the mistake recovery.

Above-mentioned SR-ARQ process shows that the value of t-Reordering timer is actually rlc layer and waits for the time of MAC layer by the grouping of HARQ retransmission mechanism retransmission of lost.The value of t-Reordering timer has very big influence to the performance of system, makes a concrete analysis of as follows:

1) value of t-Reordering timer is too small.If it is too small that the value of t-Reordering timer is provided with, will cause RLC recipient to send STATUS grouping in advance, promptly in the process of the grouping p of HARQ retransmission of lost, send STATUS, and the RLC transmit leg can retransmit p after receiving STATUS.Therefore, too small timer value will cause unnecessary retransmission, and this not only can duplicate grouping the recipient, can waste channel resource simultaneously, increase the energy consumption of transmit leg.

2) value of t-Reordering timer is excessive.If it is excessive that the value of t-Reordering timer is provided with, to cause RLC recipient's delayed delivery STATUS, thereby make the grouping of retransmission of lost in time of RLC transmit leg, this can increase the time delay of the interface aloft of grouping, and refitting (reassemble) time delay of grouping, influence upper strata host-host protocol and enforcement performance of services and postpone a meeting or conference when increasing.

Summary of the invention

Goal of the invention: at the problem and shortage of above-mentioned existing existence, the purpose of this invention is to provide a kind of adaptive error detection method that is used for cell mobile communication systems, this method can detect the Radio Link packet loss accurately and timely.

Technical scheme: for achieving the above object, the technical solution used in the present invention is: a kind of adaptive error detection method that is used for cell mobile communication systems comprises the steps:

(1) in the radio link control layer entity, is used to calculate the T in the time interval of adjacent two protocol Data Units that receive respectively _ISample, be used to realize the T of filtering _ISmoothly, in media access control layer, be used to obtain the round-trip delay of each protocol Data Unit the RTT sampling, be used to realize the RTT of filtering is level and smooth and be used to obtain the number of retransmissions of each mistake protocol Data Unit the k sampling, be used to realize that the k of filtering is level and smooth;

(2) timeout value of resetting timer is set;

T in the described step (1) _ISampling, T _ISmoothly comprise the steps:

1) T _ISampling: the radio link control layer entity is whenever received the radio link control layer protocol data cell that a new sequence number is x, writes down the time of reception t of this protocol Data Unit _Pr1, when receiving next control sub layer of wireless link protocol Data Unit,, then write down the time of reception t of this protocol Data Unit if the sequence number of this protocol Data Unit is x+1 _Pr2, calculate T simultaneously _IA sample be t _Pr1-t _Pr2

2) T _ISmoothly: calculate level and smooth T according to following formula _IValue:

$\stackrel{\‾}{{\stackrel{\‾}{T}}_I}(n+1)=\mathrm{\β}\·\stackrel{\‾}{{\stackrel{\‾}{T}}_I}\left(n\right)+(1-\mathrm{\β})\·T_I(n+1),\stackrel{\‾}{{\stackrel{\‾}{T}}_I}\left(0\right)=0,$ 0≤β≤1，

In the formula,

Be respectively n+1 constantly and the protocol Data Unit time of reception interval behind constantly level and smooth of n, β is T _ISmoothing factor, T _I(n+1) the protocol Data Unit time of reception that records constantly for n+1 sample at interval;

RTT sampling in the described step (1), RTT smoothly comprise the steps:

A) RTT sampling: positive acknowledgement/Negative Acknowledgement of the every transmission of hybrid automatic repeat request process, the transmitting time t of record positive acknowledgement/Negative Acknowledgement _Ps, when receiving next protocol Data Unit, write down the time of reception t of this protocol Data Unit _Pr, a sample that calculates RTT is t _Pr-t _Ps, and this RTT sample is uploaded to mixes automatic repeat requests entity;

B) RTT is level and smooth: mix automatic repeat requests entity and whenever receive a steps A) in the RTT sample, just utilize following formula to calculate level and smooth RTT value, and result of calculation be uploaded to the radio link control layer entity:

$\stackrel{\‾}{\stackrel{\‾}{\mathrm{RTT}}}(n+1)=\mathrm{\α}\·\stackrel{\‾}{\stackrel{\‾}{\mathrm{RTT}}}\left(n\right)+(1-\mathrm{\α})\·\mathrm{RTT}(n+1),\stackrel{\‾}{\stackrel{\‾}{\mathrm{RTT}}}\left(0\right)=0,$ 0≤α≤1，

In the formula,

Be respectively the n+1 moment and n level and smooth round-trip delay constantly, α is the smoothing factor of RTT, the sample of the round-trip delay that RTT (n+1) records constantly for n+1;

K sampling in the described step (1), k smoothly comprise the steps:

A) k sampling: when hybrid automatic repeat request process is checked through a protocol data unit error for the first time, the number of retransmissions k of this protocol Data Unit correspondence is put 0, whenever receive the once re-transmission of this protocol Data Unit afterwards, k adds 1, retransmits success or reaches maximum retransmission R up to this protocol Data Unit _MaxAfter, the k value is uploaded to the automatic repeat requests entity of mixing;

B) k is level and smooth: mix automatic repeat requests entity and whenever receive a k value in the step a), just utilize following formula to calculate level and smooth k value, and result of calculation is uploaded to the radio link control layer entity:

$\stackrel{\‾}{\stackrel{\‾}{k}}(n+1)=\mathrm{\γ}\·\stackrel{\‾}{\stackrel{\‾}{k}}\left(n\right)+(1-\mathrm{\γ})\·k(n+1),\stackrel{\‾}{\stackrel{\‾}{k}}\left(0\right)=1,$ 0≤γ≤1，

In the formula, Be respectively the n+1 moment and the n automatic repeat requests protocol Data Unit of level and smooth mixing number of retransmissions constantly, the sample of the automatic repeat requests protocol Data Unit of the mixing number of retransmissions that k (n+1) records constantly for n+1, γ is the smoothing factor of k;

Described step (2) comprising:

When the radio link control layer entity detects out-of-sequence protocol Data Unit, calculate and be provided with the timeout value of resetting timer according to following formula:

$T_R^{*}\left(n\right)=(\stackrel{\‾}{k}\left(n\right)+1)\·\stackrel{\‾}{\mathrm{RTT}}\left(n\right)-2\stackrel{\‾}{T_I},1\≤\stackrel{\‾}{k}\left(n\right)\≤R_{\max },$

In the formula,

Attach most importance to and arrange the timeout value of timer.

Beneficial effect: the present invention estimates the protocol Data Unit (PDU of MAC layer by self adaptation, Protocol Data Unit) the re-transmission time, optimize the value of the t-Reordering of SR-ARQ, thereby detect the grouping that the MAC layer is lost accurately and timely, thereby avoid the unnecessary retransmission of RLC, and reduce the retransmission delay time of grouping.Implementation complexity of the present invention is low, does not increase the expense of Radio Link air interface.

Description of drawings

Fig. 1 is the SR-ARQ schematic diagram of RLC;

Fig. 2 is transmit leg and recipient's the RLC entity and the reciprocal process schematic diagram of MAC entity;

Fig. 3 is the computational process schematic diagram of t-Recording value;

Fig. 4 is the schematic diagram of a specific embodiment of the present invention.

Embodiment

Below in conjunction with the drawings and specific embodiments, further illustrate the present invention, should understand these embodiment only is used to the present invention is described and is not used in and limit the scope of the invention, after having read the present invention, those skilled in the art all fall within the application's claims institute restricted portion to the modification of the various equivalent form of values of the present invention.

As shown in Figure 2, successfully arrive the recipient after No. 4 PDU retransmit twice (transmitting three times) by one of them process.Among Fig. 2

For the recipient correctly receives time of No. 4 PDU, therefore, for avoid t-Reordering too early or delay overtime, in Fig. 2 example, the optimal value of TR

For:

$T_R^{2*}={\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000043278950000011.png"\; state="\{\{state\}\}">t</figure-callout>}}_2^{*}-t_1---\left(1\right)$

Further, as shown in Figure 2,

$T_R^{2*}={\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA0000043278950000011.png"\; state="\{\{state\}\}">t</figure-callout>}}_2^{*}-{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HDA0000043278950000021.png"\; state="\{\{state\}\}">t</figure-callout>}}_1=3\mathrm{RTT}-{2T}_I---\left(2\right)$

For situation more generally, a HARQ PDU takes place to retransmit k time successfully after the mistake, has:

$T_R^{*}=(k+1)\&CenterDot;\mathrm{RTT}-{2T}_I---\left(3\right)$

In formula (3), RTT is the round-trip delay of a PDU of HARQ process transmission, T _IReceive the time interval of adjacent two PDU for the RLC entity.RTT and T _IProcessing time with the size of wireless channel speed, available resources block gap, Resource Block, PDU is relevant, and k is also relevant with coded system with wireless channel state, corresponding modulation simultaneously.Although RTT, T _IWith the sample of k can be by measuring, but because the time-varying characteristics of wireless channel and dynamic resource scheduling algorithm, RTT, T _IBecome when being with k.Therefore, we need through type (4), formula (5) and formula (6) to RTT, T _ICarry out smoothing processing with k.

$\stackrel{\&OverBar;}{\mathrm{RTT}}(n+1)=\mathrm{\&alpha;}\&CenterDot;\stackrel{\&OverBar;}{\mathrm{RTT}}\left(n\right)+(1-\mathrm{\&alpha;})\&CenterDot;\mathrm{RTT}(n+1),\stackrel{\&OverBar;}{\mathrm{RTT}}\left(0\right)=0,$ 0≤α≤1，(4)

$\stackrel{\&OverBar;}{T_I}(n+1)=\mathrm{\&beta;\&alpha;}\&CenterDot;\stackrel{\&OverBar;}{T_I}\left(n\right)+(1-\mathrm{\&beta;})\&CenterDot;T_I(n+1),\stackrel{\&OverBar;}{T_I}\left(0\right)=0,$ 0≤β≤1，(5)

$\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{k}}(n+1)=\mathrm{\&gamma;}\&CenterDot;\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{k}}\left(n\right)+(1-\mathrm{\&gamma;})\&CenterDot;k(n+1),\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{k}}\left(0\right)=1,$ 0≤γ≤1，(6)

In formula (4),

Be respectively n+1 constantly and the round-trip delay (smoothly finger passes through a low-pass filtering, and sample value is carried out " on average ") behind constantly level and smooth of n, the sample of the round-trip delay that RTT (n+1) records constantly for n+1, α are the smoothing factor of RTT.

In formula (5),

Be respectively n+1 constantly and the PDU time of reception interval behind constantly level and smooth of n, T _I(n+1) the PDU time of reception that records constantly for n+1 sample at interval, β is T _ISmoothing factor.

In formula (6), Be respectively the n+1 moment and n level and smooth HARQ PDU number of retransmissions constantly, the sample of the HARQ PDU number of retransmissions that k (n+1) records constantly for n+1, γ are the smoothing factor of k.

The value of above-mentioned α, β, γ can be set up on their own as the case may be by the user.

To RTT, T _IAfter carrying out smoothing processing with k, we obtain n constantly Estimated value For:

$T_R^{*}\left(n\right)=(\stackrel{\&OverBar;}{k}\left(n\right)+1)\&CenterDot;\stackrel{\&OverBar;}{\mathrm{RTT}}\left(n\right)-2\stackrel{\&OverBar;}{T_I},1\&le;\stackrel{\&OverBar;}{k}\left(n\right)\&le;R_{\max },---\left(7\right)$

In the formula, R _MaxMaximum retransmission for the MAC regulation.

As shown in Figure 3, the setting up procedure of t-Reordering timer value is finished by the recipient, relate to the recipient MAC HARQ entity, HARQ process and RLC entity (HARQ process, HARQ entity are at 3GPP TS 36.321[2] in the functional entity of MAC layer of definition, the RLC entity is at 3GPPTS 36.322[3] in the functional entity of rlc layer of definition), comprise the RTT and the k sampling of HARQ process, the RTT and the k of HARQ entity are level and smooth, the T of RLC entity _ISampling, level and smooth, and the setting of t-Reordering timer value.

The RTT sampling function of HARQ process is used to obtain the round-trip delay of each PDU, and the specific implementation process is as follows: ACK/NACK of the every transmission of HARQ, the transmitting time t of record ACK/NACK _Ps, when receiving next PDU, write down the time of reception t of this PDU _Pr, a sample that calculates RTT is t _Pr-t _Ps, and this RTT sample is uploaded to the HARQ entity.

The RTT smoothing function of HARQ entity is to realize a simple filter function, promptly whenever receives a RTT sample from the HARQ process, just utilizes formula (4) to calculate level and smooth RTT value, and result of calculation is uploaded to the RLC entity.

The k sampling function of HARQ process is used to obtain the number of retransmissions of each mistake PDU, when the HARQ receiving process is checked through a PDU mistake for the first time, the number of retransmissions k of this PDU correspondence is put 0, whenever receive the once re-transmission of this PDU afterwards, k adds 1, after this PDU retransmits success or reaches maximum retransmission, the k value is uploaded to the HARQ entity.

The k smoothing function of HARQ entity is that number of retransmissions k is carried out Filtering Processing, promptly whenever receives a k sample from the HARQ process, just utilizes formula (5) to calculate level and smooth k value, and result of calculation is uploaded to the RLC entity.

The sampling smoothing function of the TI of RLC entity is used for the time interval that the RLC receiving entity calculates adjacent two PDU that receive, and detailed process is as follows: whenever receive the RLC PDU that a new sequence number is x, write down the time of reception t of this PDU _Pr1, when receiving next RLC PDU,, then write down the time of reception t of this PDU if the sequence number of this PDU is x+1 _Pr2, calculate T simultaneously _IA sample be t _Pr1-t _Pr2, calculate level and smooth T according to formula (6) at last _IValue.

The major function that t-Reordering is provided with functional block is when RLC detects out-of-sequence PDU, according to current T _I, RTT and k value (promptly

), utilize formula (7) to calculate and be provided with the timeout value of timer t-Reordering.

Fig. 4 is the embodiment that the present invention is used for the LTE system of 3GPP.Ellipse among Fig. 4 is represented service access point, it is the interface between the protocol layer up and down in the agreement, business datum is at logic channel DTCH (Dedicated Traffic Channel, Dedicated Traffic Channel), DL-SCH (DownLink Shared Channel, DSCH Downlink Shared Channel), UL-SCH (Uperlink Shared Channel, Uplink Shared Channel) channel; Logic channel DCCH (Dedicated Control Channel, Dedicated Control Channel) is used for control information transmission; Bgical channel priority is distinguished function and multiplexing and demultiplexing function at 3GPPTS36.321[2] in define, multiplexing, the demultiplexing of main completion logic channel (comprising Dedicated Control Channel and Dedicated Traffic Channel), and the logic channel different according to the priority scheduling of channel.

In Fig. 4,4 functions of this patent (comprise RTT, k sampling function, RTT, k smoothing function, the sampling smoothing function of TI and t-Recording are provided with function) be embedded at 3GPPTS36.321[2 respectively] in definition the MAC layer HARQ process, HARQ entity and at 3GPPTS36.322[3] in the functional entity of the rlc layer that defines.All functions all realize that the recipient recipient can be eNB, also can be UE.Concrete enforcement is as follows:

1) RTT sampling: the round-trip delay of statistics MAC PDU, in the HARQ of MAC layer process, implement;

2) k sampling: the number of retransmissions of the MAC PDU of statistics mistake, in the HARQ of MAC layer process, implement;

3) RTT is level and smooth: according to the RTT sample value, utilize formula (4) to calculate the mean value of the round-trip delay of MAC PDU, implement in the HARQ of MAC layer entity;

4) k is level and smooth: according to the k sample value, utilize formula (5) to calculate the mean value of number of retransmissions of the MAC PDU of mistake, implement in the HARQ of MAC layer entity;

5) the TI sampling is level and smooth: statistics RLC entity receives the sample in the time interval of adjacent two PDU, and utilizes formula (6) to calculate its mean value according to sample, realizes at affirmation pattern (AM:Acknowledge Mode) the RLC entity of rlc layer;

6) t-Reordering is provided with: according to the mean value of RTT, k, TI, utilize formula (7) to calculate the value of t-Reordering, and according to result of calculation t-Reordering is set, realize at the AM of rlc layer RLC entity.

This patent has proposed in the WCDMA evolution version dynamic optimization method of PDU error detection occurs timer (t-Reordering) in the RLC entity.Avoiding the unnecessary PDU of rlc layer to retransmit, thereby avoid waste of radio resources, save energy, and reduce the propagation delay time of RLC PDU.This method is independently finished by the recipient, does not need by the mutual signaling message of air interface, realizes simple simultaneously.

Claims (1)

1. an adaptive error detection method that is used for cell mobile communication systems is characterized in that comprising the steps:

(1) in the radio link control layer entity, is used to calculate the T in the time interval of adjacent two protocol Data Units that receive respectively _ISample, be used to realize the T of filtering _ISmoothly, in media access control layer, be used to obtain the round-trip delay of each protocol Data Unit the RTT sampling, be used to realize the RTT of filtering is level and smooth and be used to obtain the number of retransmissions of each mistake protocol Data Unit the k sampling, be used to realize that the k of filtering is level and smooth;

(2) timeout value of resetting timer is set;

T in the described step (1) _ISampling, T _ISmoothly comprise the steps:

1) T _ISampling: the radio link control layer entity is whenever received the radio link control layer protocol data cell that a new sequence number is x, writes down the time of reception t of this protocol Data Unit _Pr1, when receiving next control sub layer of wireless link protocol Data Unit,, then write down the time of reception t of this protocol Data Unit if the sequence number of this protocol Data Unit is x+1 _Pr2, calculate T simultaneously _IA sample be t _Pr1-t _Pr2

2) T _ISmoothly: calculate level and smooth T according to following formula _IValue:

$\stackrel{\&OverBar;}{{\stackrel{\&OverBar;}{T}}_I}(n+1)=\mathrm{\&beta;}\&CenterDot;\stackrel{\&OverBar;}{{\stackrel{\&OverBar;}{T}}_I}\left(n\right)+(1-\mathrm{\&beta;})\&CenterDot;T_I(n+1),\stackrel{\&OverBar;}{{\stackrel{\&OverBar;}{T}}_I}\left(0\right)=0,$ 0≤β≤1，

In the formula,

Be respectively n+1 constantly and the protocol Data Unit time of reception interval behind constantly level and smooth of n, β is T _ISmoothing factor, T _I(n+1) the protocol Data Unit time of reception that records constantly for n+1 sample at interval;

RTT sampling in the described step (1), RTT smoothly comprise the steps:

A) RTT sampling: positive acknowledgement/Negative Acknowledgement of the every transmission of hybrid automatic repeat request process, the transmitting time t of record positive acknowledgement/Negative Acknowledgement _Ps, when receiving next protocol Data Unit, write down the time of reception t of this protocol Data Unit _Pr, a sample that calculates RTT is t _Pr-t _Ps, and this RTT sample is uploaded to mixes automatic repeat requests entity;

B) RTT is level and smooth: mix automatic repeat requests entity and whenever receive a steps A) in the RTT sample, just utilize following formula to calculate level and smooth RTT value, and result of calculation be uploaded to the radio link control layer entity:

$\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{\mathrm{RTT}}}(n+1)=\mathrm{\&alpha;}\&CenterDot;\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{\mathrm{RTT}}}\left(n\right)+(1-\mathrm{\&alpha;})\&CenterDot;\mathrm{RTT}(n+1),\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{\mathrm{RTT}}}\left(0\right)=0,$ 0≤α≤1，

In the formula,

Be respectively the n+1 moment and n level and smooth round-trip delay constantly, α is the smoothing factor of RTT, the sample of the round-trip delay that RTT (n+1) records constantly for n+1;

K sampling in the described step (1), k smoothly comprise the steps:

A) k sampling: when hybrid automatic repeat request process is checked through a protocol data unit error for the first time, the number of retransmissions k of this protocol Data Unit correspondence is put 0, whenever receive the once re-transmission of this protocol Data Unit afterwards, k adds 1, retransmits success or reaches maximum retransmission R up to this protocol Data Unit _MaxAfter, the k value is uploaded to the automatic repeat requests entity of mixing;

B) k is level and smooth: mix automatic repeat requests entity and whenever receive a k value in the step a), just utilize following formula to calculate level and smooth k value, and result of calculation is uploaded to the radio link control layer entity:

$\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{k}}(n+1)=\mathrm{\&gamma;}\&CenterDot;\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{k}}\left(n\right)+(1-\mathrm{\&gamma;})\&CenterDot;k(n+1),\stackrel{\&OverBar;}{\stackrel{\&OverBar;}{k}}\left(0\right)=1,$ 0≤γ≤1，

In the formula,

Be respectively the n+1 moment and the n automatic repeat requests protocol Data Unit of level and smooth mixing number of retransmissions constantly, the sample of the automatic repeat requests protocol Data Unit of the mixing number of retransmissions that k (n+1) records constantly for n+1, γ is the smoothing factor of k;

Described step (2) comprising:

When the radio link control layer entity detects out-of-sequence protocol Data Unit, calculate and be provided with the timeout value of resetting timer according to following formula:

$T_R^{*}\left(n\right)=(\stackrel{\&OverBar;}{k}\left(n\right)+1)\&CenterDot;\stackrel{\&OverBar;}{\mathrm{RTT}}\left(n\right)-2\stackrel{\&OverBar;}{T_I},1\&le;\stackrel{\&OverBar;}{k}\left(n\right)\&le;R_{\max },$

In the formula, Attach most importance to and arrange the timeout value of timer.

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